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51.
Repertoire matching occurs when one songbird replies to another with a song type that the two birds share. Repertoire matching has previously been demonstrated to occur at well above chance levels in a western population of song sparrows, where it is hypothesized to serve as a low level threat in a hierarchy of aggressive signals. Here we test for repertoire matching in an eastern population of song sparrows. Previous work indicates that this eastern population differs from the western one in having lower levels of song sharing between neighboring males and in showing no association between song sharing and territory tenure. Here we confirm that males in this eastern population on average share few whole songs with their neighbors. The eastern males are familiar with their neighbors’ repertoires, as evidenced by a stronger singing response to stranger song than to neighbor song. Males in the eastern population did not repertoire match: when played an unshared song type from a specific neighbor, they did not reply with a song type shared with that neighbor more often than expected by chance or more often than in response to playback of a control song (an unshared stranger song). The results thus demonstrate a qualitative difference in vocal signaling strategies between two populations of the same species. 相似文献
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53.
1. Pressure previously measured on the body surface of swimming bluefish were resolved into their backward vectorial components to allow calculation of profile drag. It was 0.18 kg at a speed of 1.8 m/sec. Tangential drag was calculated as if for a thin plate of an area equal to that of the fish. It was 0.08 kg at 1.8 m/sec. Net drag, 0.26 kg, was the sum of profile and tangential drag. 2. Thrust and drag also were calculated from the changes of acceleration measured during steady swimming, assuming that thrust took place only during the acceleration phase, whereas drag occurred during both acceleration and deceleration. This drag was 0.08 kg at a speed of 1.1 m/sec. It is compatible with the drag of 0.26 at 1.8 m/sec calculated from profile and tangential drag provided drag varies as the square of velocity. 3. The force required to produced maximal acceleration was measured during a scare. It was calculated to be 6.9 kg at a peak acceleration of 3 g. 4. The compression strength of th vertebrae was found to be approximately 20 kg per cm2, or roughly three times the force encountered during maximal acceleration. This safety factor of 3 would be reduced when the back was curved, or if opposing groups of muscles were under tension. 5. The finding that a bluefish can accelerate at 3 g and that the vertebral column is strongg enough to withstand this force indicates that the muscles and body structure of a bluefish would be able to withstand the force of gravity if the fish were otherwise equipped for terrestrial life. This fish may have evolved these strengths simultaneously with land animals. It is speculated that other fish may have evolved some degree of strength to overcome inertia and drag during aquatic locomotion, and this evolution may have been a prelude to terrestrial locomotion. 相似文献
54.
55.
Alveolar resistance to atelectasis 总被引:4,自引:0,他引:4
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57.
Daikoku T Matsumoto H Gupta RA Das SK Gassmann M DuBois RN Dey SK 《The Journal of biological chemistry》2003,278(9):7683-7691
Increased uterine vascular permeability and angiogenesis are hallmarks of implantation and placentation. These events are profoundly influenced by vascular endothelial growth factor (VEGF). We previously showed that VEGF isoforms and VEGF receptors are expressed in the uterus, suggesting the role of VEGF in uterine vascular permeability and angiogenesis required for implantation and decidualization. We have recently shown that estrogen promotes uterine vascular permeability but inhibits angiogenesis, whereas progesterone stimulates angiogenesis with little effect on vascular permeability. However, the mechanism of differential steroid hormonal regulation of uterine angiogenesis remains unresolved. Oxygen homeostasis is essential for cell survival and is primarily mediated by hypoxia-inducible factors (HIFs). These factors are intimately associated with vascular events and induce VEGF expression by binding to the hypoxia response element in the VEGF promoter. HIFalpha isoforms function by forming heterodimers with the aryl hydrocarbon nuclear translocator (ARNT) (HIF-beta) family members. There is very limited information on the relationship among HIFs, ARNTs, and VEGF in the uterus during early pregnancy, although the role of HIFs in regulating VEGF and angiogenesis in cancers is well documented. Using molecular and physiological approaches, we here show that uterine expression of HIFs and ARNTs does not correlate with VEGF expression during the preimplantation period (days 1-4) in mice. In contrast, their expression follows the localization of uterine VEGF expression with increasing angiogenesis during the postimplantation period (days 5-8). This disparate pattern of uterine HIFs, ARNTs, and VEGF expression on days 1-4 of pregnancy suggests HIFs have multiple roles in addition to the regulation of angiogenesis during the peri-implantation period. Using pharmacological, molecular, and genetic approaches, we also observed that although progesterone primarily up-regulates uterine HIF-1alpha expression, estrogen transiently stimulates that of HIF-2alpha. 相似文献
58.
Croft KE Dalby AB Hogan DJ Orr KE Hewitt EA Africa RJ DuBois ML Prescott DM 《Journal of molecular evolution》2003,56(3):341-350
Abstract
The nucleotide sequences of 16 newly reported and 8 previously reported actin-encoding macronuclear DNA molecules in spirotrichs
have been compared. As described for the eight previously reported molecules, the first 50 bases (noncoding) inside the telomere
at both 5′ strands in additional actin molecules are purine-rich. This anomalous base composition might serve as a signal
to identify macronuclear molecules in micronuclear DNA during development. The 50-base segment upstream of the ATG in the
5′ leaders of the actin molecules contains extensive, conserved sequence motifs that are possibly promoter elements. The 3′
noncoding trailers contain virtually no conserved sequence motifs. With one exception, the 3′ trailers contain a second stop
codon (TGA) 36 bases on average downstream of the primary stop codon. Excluding Moneuplotes crassus, amino acid identities in actin I range from 78 to 100%, with variations distributed nonrandomly along the sequence. Phylogenetic
trees based on the actin nucleotide sequences of 22 spirotrichs define the evolutionary relationships of their actin-encoding
molecules. The actin phylogeny, while well supported by posterior probabilities, does not always coincide with the phylogeny
defined in rDNA analyses or classical taxonomic classifications. 相似文献
59.
60.
N-Linked glycosylation of a baculovirus-expressed recombinant glycoprotein in insect larvae and tissue culture cells 总被引:5,自引:3,他引:2
The potential of insect cell cultures and larvae infected with recombinant
baculoviruses to produce authentic recombinant glycoproteins cloned from
mammalian sources was investigated. A comparison was made of the N-linked
glycans attached to secreted alkaline phosphatase (SEAP) produced in four
species of insect larvae and their derived cell lines plus one additional
insect cell line and larvae of one additional species. These data survey
N-linked oligosaccharides produced in four families and six genera of the
order Lepidoptera. Recombinant SEAP expressed by recombinant isolates of
Autographa californica and Bombyx mori nucleopolyhedroviruses was purified
from cell culture medium, larval hemolymph or larval homogenates by
phosphate affinity chromatography. The N-linked oligosaccharides were
released with PNGase-F, labeled with 8- aminonaphthalene-1-3-6-trisulfonic
acid, fractionated by polyacrylamide gel electrophoresis, and analyzed by
fluorescence imaging. The oligosaccharide structures were confirmed with
exoglycosidase digestions. Recombinant SEAP produced in cell lines of
Lymantria dispar (IPLB-LdEIta), Heliothis virescens (IPLB-HvT1), and Bombyx
mori (BmN) and larvae of Spodoptera frugiperda, Trichoplusia ni ,
H.virescens , B.mori , and Danaus plexippus contained oligosaccharides that
were structurally identical to the 10 oligosaccharides attached to SEAP
produced in T.ni cell lines. The oligosaccharide structures were all
mannose-terminated. Structures containing two or three mannose residues,
with and without core fucosylation, constituted more than 75% of the
oligosaccharides from the cell culture and larval samples.
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